Detailed discussions of absorbent articles employing superabsorbent materials in disposable diapers and other products are included in Pieniak et al. U.S. Pat. Nos. 4,500,315, 4,540,454, 4,537,590, and 4,573,988, which collectively provide useful background for this invention.
As discussed in the Pieniak et al. patents noted above, absorbent articles can be advantageously made with absorbing layers and wicking layers. The absorbing layers can be advantageously made from polyester fibers, within which particles of superabsorbent material are dispersed. The wicking layers can be advantageously made from cellulosic fibers, which can include or be provided in the form of a densified, paper-like layer, such as is disclosed in Burgeni U.S. Pat. No. 3,017,304, on one side or each side. See, also, Mesek et al. U.S. Pat. No. 3,612,055 and Repke U.S. Pat. No. 3,938,522.
As also discussed in the Pieniak et al. patents noted above, the superabsorbent material can be advantageously formed from a polymerizable, cross-linkable material, e.g., a water-soluble monomer exemplified by sodium, potassium, or ammonium acrylate, which is coated, in a liquid carrier, e.g., in an aqueous solution, onto a fibrous web, and which is polymerized and cross-linked in situ, so as to form a hydrophilic polymer, which has superabsorbent properties.
Conventional coating techniques involve flooding the fibrous web with the material, in the liquid carrier, while the fibrous web is supported on a screen, so as to saturate the fibrous web, and exposing the saturated web to a partial vacuum, which removes excess amounts of the material, in the liquid carrier. It has been heretofore known to remove excess amounts of liquid by means of a padder or squeeze roll, after the fibrous web has been saturated, with similar results.
As an alternative to conventional coating techniques discussed above, it has been heretofore known to spray droplets of such a material, in a liquid carrier, by means of nozzles.
It also has been heretofore known that polymerization and cross-linking in situ can be advantageously effected by electron beam irradiation. Other techniques for polymerizing and cross-linking have been heretofore known, e.g., chemical initiation, which may require a catalyst or initiator of a known type, and heating by conventional heating means.
Although the Pieniak et al. patents noted above disclose useful products and useful methods of manufacturing such products, there has been a need, heretofore, for absorbent articles offering superior wicking and absorbent properties.
Herein, each reference to a polymerizable, cross-linkable material, in a liquid carrier, is intended to refer to any suitable monomer, oligomer, or polymer of low molecular weight, as exemplified by but not limited to a sodium, potassium, or ammonium salt of acrylic or methacrylic acid, together with a sufficient quantity of any catalyst or initiator needed to catalyze or initiate polymerizing and cross-linking of the monomer, oligomer, or polymer of low molecular weight, in a solution or suspension in a liquid carrier, as exemplified by but not limited to water. Moreover, as and where appropriate, each reference to a polymer is intended to refer to a heteropolymer or a polymer of a usual structure.
Herein, each reference to a material having absorbent properties is intended to refer to a material capable of absorbing liquid human excreta, such as urine, menses, or wound excreta. Moreover, each reference to a material having superabsorbent properties is intended to refer to a material capable of absorbing many times its own weight of such human excreta.